Copper hydroxide is a technically important starting material which is mainly used as an active constituent of fungicidal and insecticidal compositions. Other fields of application are baths for the electrodeposition of copper and as a starting material for making catalysts. Copper hydroxide serves also as a reactive starting material in the production of other copper salts, such as copper arsenate for use in wood preservatives.
It is known to produce copper hydroxide in a two-stage process from a previously produced copper salt, such as copper sulfate, copper carbonate or copper oxychloride, in a process in which alkalies are used to effect a precipitation of copper hydroxide usually at a temperature below 20.degree. C. (U.S. Pat. Nos. 3,635,668 and 4,490,337, European Patent No. 80,226).
These processes have the disadvantage that copper salt is always required as an intermediate product and that the use of alkalies as a precipitant will result in the formation of large quantities of waste water, which must be treated before it can be disposed of.
U.S. Pat. No. 2,536,096 discloses a single-stage process in which copper hydroxide is produced directly from scrap copper in a solution of ammonia in concentrations in excess of 10 g/l of soluble ammonium and preferably in excess of 30 g/l.
The resulting hydroxide first deposits on the copper surface and must continuously be removed by friction.
This process has other disadvantages as well. Only high concentrations of ammonia will ensure sufficiently high reaction rates. For this reason, a washer or a totally enclosed reaction vessel will be required. Besides, the product still contains substantial quantities of ammonia, which must be washed out by means of large quantities of water. Moreover, the use of ammonia results in pollution at the work place and in the environment.